Error running script: Error evaluating expression 'GetAllChildObjects(game.pov)': Collection was modified; enumeration operation may not execute.
I am not working with lists myself. I am not sure what the "foreach" means. I especially do not know what "foreach over" means.
What can be causing this? Where should I look?

Error running script: Error evaluating expression 'ListCombine(ScopeReachableNotHeldForRoom(room), ScopeReachableInventory())': Value cannot be null.Parameter name: collection
Error running script: Unrecognised list type
Error running script: Error evaluating expression 'ListCombine(ScopeReachableNotHeldForRoom(room), ScopeVisibleNotReachableForRoom(room))': Value cannot be null.Parameter name: collection
Error running script: Cannot foreach over '' as it is not a list
Error running script: Error evaluating expression 'ListExclude(ScopeVisibleNotHeldNotScenery(), game.pov)': Object reference not set to an instance of an object.

That looks like the code that generates the item list for the places and objects pane.

Have you changed the value of game.pov? Or destroyed the player object?

The most common cause for a torrent of errors like this is attempting to move the player to null or "". But the first error stands out, because it isn't looking at the room. So I wonder if it's the player object itself that's set to something other than an object.

If you're using ChangePOV (something) or game.pov = something, make sure that your something is actually an object, and hasn't been destroyed. Otherwise, check the game's "player" tab and make sure that the player object is set to a valid object (although the core scripts should check this at the start of the game)

If that doesn't help, could you share the game so I can try to track down the issue?

Tell me how to share the game and I will.
I am working offline, though, so I might not be able to share it.

I do know it runs a list of "editing in code view, when I am not doing anything in code view, whenever I am inactive for a very long period of time, and that always bothers me. It makes it difficult to arrow back the undo button to the point the game needs to be undone to, when it does.
I am still looking for the empty tab, or the unfinished script.
I tried to mail you the game's code, but it was too long for the mailing system.

I might add the last pictures and sound effects, then upload it so people can copy and paste me any error messages, and then, I'll try to fix it a little at a time, if I can find the causes.

Here is a potential clue
I got a debug notice when publishing the game offline, last night, but not this afternoon.
[0727/231333:ERROR:renderer_main.cc(207)] Running without renderer sandbox
[0727/231334:ERROR:cache_util_win.cc(20)] Unable to move the cache: 5
[0727/231334:ERROR:cache_util.cc(132)] Unable to move cache folder C:\Users\wrenj\AppData\Local\Temp\GPUCache to C:\Users\wrenj\AppData\Local\Temp\old_GPUCache_000
[0727/231334:ERROR:cache_creator.cc(132)] Unable to create cache
[0727/231334:ERROR:shader_disk_cache.cc(588)] Shader Cache Creation failed: -2
[0727/231334:ERROR:cache_util_win.cc(20)] Unable to move the cache: 5
[0727/231334:ERROR:cache_util.cc(132)] Unable to move cache folder C:\Users\wrenj\AppData\Local\Temp\ to C:\Users\wrenj\AppData\Local\old_Temp_000
[0727/231334:ERROR:cache_creator.cc(132)] Unable to create cache
[0727/231401:WARNING:message_in_transit_queue.cc(18)] Destroying nonempty message queue

That looks like a Chrome error to me; unlikely to be related.